Which type of fire is specifically designed to impede enemy movement across defensive lines?

Final Protective Fire (FPF) is a type of fire mission that is specifically designed to provide immediate and effective fire support to prevent enemy forces from breaching defensive positions. The primary purpose of FPF is to create a barrier of fire that can disrupt and hinder the movement of an attacking enemy, ensuring that they cannot penetrate through the defensive lines that are being held.

By employing FPF, commanders aim to maximize the effects of artillery or indirect fires on an enemy force that is expected to attack, particularly close to friendly troops. This type of fire is executed not only to deter the enemy but also to protect friendly forces from harm, allowing them to hold their ground.

In contrast, other types of target designations serve different purposes. Priority targets may be about neutralizing critical enemy assets, while immediate suppression refers to quickly engaging known threats without the specific intent of creating a fire barrier. On-call targets offer flexibility for future engagements rather than focusing on immediate hindrance to enemy maneuvers. Thus, the unique function of Final Protective Fire in securing defensive lines makes it the most fitting choice for this context.